Dedicated / smart fuel inserters.
Explanation
When you want to put fuel in trains, you have to use the inserters. It works, but there is a problem if they are not correctly positioned or when train sizes, especially train with more locomotives, differ. The problem is that inserters do not know what they are inserting into, or out of. It is my assumption that that is one of the reasons that since version 0.15.7 of Factorio, inserters can no longer extract fuel from a Locomotive, to prevent them from emptying fuel from a train on accident. (Link: https://wiki.factorio.com/Version_history/0.15.0#0.15.7). (small caveat: inserters can still remove Used Fuel from locomotives, according to the patch notes, but I don't think this is used normally).
Now, what if the inserters knew that they have to work only on fuel?
Request / Proposal
Optionally make inserters only work on the fuel contents of a train, not on its other content.
The way I could see this working is by one of these methods:
- Have an extra setting for inserters, besides currently Overriding Stack Size, that this inserter is for Fuel Only
- Have a new dedicated inserter entity, that can only work with Fuel content
- Automatically insert fuel into Cars and Tanks parked against the inserter.
- Insert new fuel in, but also remove old fuel. (remove Coal from fuel and replace with Rocket Fuel)
- Fuel trains with more than one locomotive. (it will automatically skip wagons, and only load Locomotives on fuel)